Octacalcium phosphate

Octacalcium phosphate (sometimes referred to as OCP) is a calcium phosphate with a formula Ca8H2(PO4)6.5H2O.[1] OCP may be a precursor to tooth enamel, dentine, and bones.

Octacalcium phosphate
Names
IUPAC name
octacalcium dihydrogen hexakis(phosphate) pentahydrate
Other names
Octacalcium Phosphate
Identifiers
Properties
Ca8H2(PO4)6.5H2O
Molar mass 446.234023 g/mol
Appearance white powder
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

OCP is a precursor of hydroxylapatite (HAP), an inorganic biomineral that is important in bone growth.[2] OCP has been suggested as a replacement for HAP in bone grafts.[3][4][5]

Crystal structure

OCP has the lattice constants a = 19.7 A., b = 9.59 A., c =6.87 A., α≅β = 90.7’ and γ = 71.8’. Corresponding hydroxyapatite constants are 2a = 18.84 A., a’ = 9.42 A., c = 6.885 k., α = α’ = 90” and γ = 60”, resemble closely those of OCP in the values of b, c and a, which lie in the plane of the OCP plates. The final pattern was apatitic, intermediate in sharpness between those of tooth enamel and bone. Boiling water decomposed OCP into an apatite approaching hydroxyapatite in composition, along with a variable amount of CaHP04. Both thermal and hydrothermal treatments sometimes yielded apatitic single crystal pseudomorphs after OCP, the c-axes being parallel to the c of the original OCP.[2] Due to the small crystal structure of OCP it is often a twinned crystal structure. The average crystal size of OCP is 13.5 ± 0.2 nm [6]

Synthesis

It can be prepared by treating calcium acetate with sodium acid phosphate solution.[6][7]

Hydrolysis of OCP creates hydroxyapatite [6]

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References
  1. Reacquel Z. LeGeros "Preparation of octacalcium phosphate (OCP): A direct fast method", Journal Calcified Tissue International, Volume 37, Number 2, March 1985, pp.194-197.(abstract)
  2. Brown, W. E., Lehr, J. R.. Smith, J. P., Frazier, A. W., J. Am. Chem. Soc., 1957, 79 (19), 5318.
  3. Brown, W.E., Eidelman, N., Tomazic, B., 1987. Adv. Dent. Res., 1; 306
  4. Nelson, D.J.A., McLean, J.D., 1984. Calcif Tissue Int. 36, 219.
  5. http://www.pubmed.gov Octacalcium phosphate: Osteoconductivity and crystal chemistry. Suzaki, O. Last accessed 4/09/10
  6. M.J. Arellano-Jiménez, M. J., García-García, R., Reyes-Gasga, R. 2009. Journal of Physics and Chemistry of Solids 70, 390.
  7. LeGeros, R. Z., 1985. Calcif Tissue Int 37:194

Sources
  • Laurence C. Chow, Edward D. Eanes, "Octacalcium phosphate", Monograph in Oral Science, S. Karger AG, 2001, ISBN 978-3-8055-7228-6.(Google books)
  • Brown, W. E., Lehr, J. R.. Smith, J. P., Frazier, A. W., J. Am. Chem. Soc., 1957, 79 (19), 5318.
  • M.J. Arellano-Jiméneza, M. J., García-Garcíaa, R., Reyes-Gasga, R. 2009. Journal of Physics and Chemistry of Solids 70, 390.
  • LeGeros, R. Z., 1985. Calcif Tissue Int 37:194
  • https://pubchem.ncbi.nlm.nih.gov Summary octacalcium phosphate. Last accessed 4/9/10
  • www.pubmed.gov Octacalcium phosphate: Osteoconductivity and crystal chemistry. Suzuki, O. Last accessed 4/09/10
  • Nelson, D.J.A., McLean, J.D., 1984. Calcif Tissue Int. 36, 219.
  • Brown, W.E., Eidelman, N., Tomazic, B., 1987. Adv. Dent. Res., 1; 306
  • http://www.ccmr.cornell.edu/facilities/Winners06Sum/dattran.html Cornell Center for Materials Research. Dat T. Tran. Last Accessed 4/09/10
  • Komlev, V. S., Barinov, S. M., Bozo, I. I., Deev, R. V., Eremin, I. I., Fedotov, A. Y., ... & Zorin, V. L. Bioceramics composed of octacalcium phosphate demonstrate enhanced biological behavior // ACS Applied Materials & Interfaces. 2014. V. 6.(19). P. 16610-16620.
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